A 2.1-magnitude earthquake was recorded at 9:04 a.m. Friday, three kilometers east of the Conning Towers at Nautilus Park in Groton, said Jana Pursley, a geophysicist with the U.S. Geological Survey.
A second, 2.2-magnitude earthquake was recorded at 9:42 a.m. Friday, about a kilometer northeast of Ledyard Center, she said.
The low-magnitude earthquakes caused no injuries. There were no reports of damage.
“Yep … it was an earthquake,” First Selectman Ed Haberek said in a Facebook post Monday.
He included a record of the seismic activity on his Facebook wall. The depiction is from the Weston Observatory at Boston College, he said, which contacted him Monday.
“Small earthquakes at a very shallow depth are commonly heard and reported as sounding like explosions,” he wrote.
The explosive sounds startled area residents, including people in Old Mystic section of Stonington. Police and firefighters responded and searched for signs of an explosion but found none.
Residents reported that their houses shook from the booms.
“People are out looking at their chimneys,” said Nancy Peta of Main Street said Friday. “It’s very mysterious.”
She said the booming sounds started about 9:15 a.m. The first was a deep, explosive sound that sounded as though a propane tank blew up, she said. But there was no smoke, she said.
The second boom was not as loud, but the third was the worst, she said.
“It was physical. You could feel it through your body,” she said.
She called 911 for the second time after that the third boom, she said.
By Christine Dempsey, Hartford Courant
FOX CT Meteorologist Joe Furey contributed to this report.